/Engine/Source/Runtime/NavigationSystem/Public/NavigationSystem.h
Returns the world default navigation data instance. Creates one if it doesn't exist.
[ANavigationData](API\Runtime\NavigationSystem\ANavigationData) * GetDefaultNavDataInstance ( [FNavigationSystem::ECreateIfMissing](API\Runtime\NavigationSystem\FNavigationSystem__ECreateIfMiss-) CreateNewIfNoneFound )